1. Technical Field
The inventive concept relates to a semiconductor device, and more particularly, to a vertical type semiconductor device, a fabrication method thereof, and an operation method thereof.
2. Related Art
With demands on semiconductor devices with ultra-high integration, ultra-high speed, and ultra-low power applied to electronic apparatuses which are increasingly miniaturized, vertical type memory devices have been actively studied.
In recent years, the resistive memory devices are drawing attention as next-generation memory devices and have adopted the vertical structure. The resistive memory devices select cells through access devices. The resistive memory devices are devices configured to store data by changing a resistance state of a data storage material electrically connected thereto. As an example of the resistive memory devices, there are phase-change random access memory devices (PCRAMs), resistive RAMs (ReRAMs), and magnetic RAMs (MRAMs).
As the access devices of the resistive memory devices, diodes or transistors are adopted. In particular, the transistors have received attention as the access device of the resistive memory devices since the transistors have a low operation voltage through controlling of a threshold voltage thereof to be lowered as compared with the diodes and the vertical structure of the transistors is adopted.
That is, there is a limit to lowering an operation voltage of the diodes since a voltage of above 1.1 V has to be applied to the diodes. When the diodes are formed on a word line, resistance of the word line is changed according to a location of cell to cause word line bouncing.
A reduction rate of the transistors having a horizontal structure is limited but the vertical transistors may ensure sufficient current drivability in a restricted area. Further, the vertical transistors may improve a voltage drop component due to an external resistor through reduction in a source resistance.
On the other hand, the access devices such as the diodes and the transistors are formed using a semiconductor substrate as a base. In recent years, the semiconductor memory devices are formed in multiple layers to obtain high integration. When the access devices are formed using the semiconductor substrate as a base, it is impossible to stack several layers.